First, there are more than 300 players on all systems.
Some people may not play much anymore but they like to keep up-to-date on the game in case they get back into it. Plus, I’m sure lots of those people subbed to him while they still played and so they get a notification when Grizzle uploads a new video and they check it out.

If I understand the SteamCharts correctly (where I think you get the 300 number), it counts the players in a certain moment (mostly in every hour), so currently the past 30 days peak was 774 which means at worst scenario there are 774 players though it would mean they are hell dedicated. It is more likely that an avarage evolve player plays roughly 10 hours per week so the avarage 354 player in an hour should be multiplied as such=> 1week=7 days=168hours => 168/10=16,8 this is the multiplier (if we say an avarage evolve players plays 84 hours then it would mean 168/84=2 because then less players could produce the same number). 354*16,8=5947 neary 6000 active player though this is a highly estimated number + given there is xbox and PS4 with nearly same numbers there is nearly 20 000 active players, offcourse, everybody plays in different time, so in PC in an avarage hour there are 354 players.

the past 30 days peak was 774 which means at worst scenario there are 774 players

actually BEST* scenario there are 774.

NeroBad:

this is a highly estimated number

it’s so estimated, that you didn’t notice on steam charts, there is the full statistics with graphics from when evolve came out, to today. 6k players in the steam charts records, are present only 3 times and they are player peaks (february 2015, march, 2015, september 2015)
your number is highly unreliable sir.